1. Field
Example embodiments relate to oscillators and methods of operating the same.
2. Description of the Related Art
Oscillators are devices that generate signals having given frequencies. Oscillators are used in a wireless communication system (e.g., a mobile phone, a satellite and radar communication device, a wireless network device, an automobile communication device), and in an analog sound synthesizer.
Main factors of an oscillator are a quality factor, an output power, and/or phase noise. As the quality factor and the output power of the oscillator increases and the phase noise of the oscillator decreases, the characteristics of the oscillator are improved. Recently, as the demand for high performance and the miniaturization of communication devices increases and the operating frequency bands of communication devices are increased, it is required to develop a high-output oscillator having a small size, a high quality factor and low phase noise.
Spin torque oscillators using a spin transfer torque phenomenon have been suggested. Spin torque oscillators can be manufactured to be much smaller than general inductor and capacitor (LC) oscillators and general film bulk acoustic resonator (FBAR) oscillators and have a relatively high quality factor and thus have drawn attention as the next generation of oscillators.
However, general spin torque oscillators require a strong magnetic field for high-frequency oscillation. For example, in order to generate the frequency of about several GHz, an external magnetic field of about several hundreds of oersted (Oe) should be applied to general spin torque oscillators. However, it is very difficult to apply such a large external magnetic field to general spin torque oscillators. Also, an additional device for applying an external magnetic field disturbs miniaturization, an advantage of spin torque oscillators.